This is a nice article covering something that I personally had to look a lot of places to learn.

I have a back for a Graflex camera that came to me with a box of other assorted Graflex parts (junk, as my wife calls it). It has 2 polished chrome sliders on it similar to but not the same as those on the Graflok back. These shiders are flat across the contacting edge, where as the Graflok sliders are "out-dented" (opposite of indented...?).

The sliders hold in place a 4x5 ground glass focusing screen mounted in a frame, with a pop-out hood. But to insert a film holder, instead of being able to slide it in beind the ground glass, you must release the sliders and remove the ground glass frame. The interesting thing is that the space where the ground glass frame is held is about 1/2 inch too tall for the 4x5 film holders (or any of the other accessory backs I have (rollfilm, Grafmatic, etc.)

So I'm not sure what this back is for. It mates to the back of the body of my Crown Graphic (I tried it) so I know it is for this family of cameras.

Sounds like you have a Gralfex back, as opposed to the more common Graphic. The Graflex back accepts the same film holder and accesories that fit cameras like the RB Graflex and were available for the Pacemaker. I have a 1950's model with such a back and they are listed in the Pacemaker catologue as an option. The GG panel is interchangeable with my RB Graflex SLR camera. Mine is excactly like the image of the back in the catalogue (the catalogue being a later version form the 1960's), and sounds like what you have with the double sliders that look sort of like a Graflok, but without the hooks for the removeable spring focus panel.
Hope that helps

That sounds like it might be it. I have no need for it... all the other accessories and holders fit the Graflok back, so it is just sitting here. It has no GG in it, so I can't even scavenge that. But it was :free" in a box of other Graflex stuff.